Correction of self-screening effect in integrating sphere-based measurement of total luminous flux of large-area surface-emitting light sources.

We present a correction method of a systematic error that arises when total luminous flux of a large-area surface-emitting light source (SLS) is measured in an integrating sphere by substitution with a reference lamp. Putting a large-area SLS into an integrating sphere is equivalent to adding a low-reflective baffle to screen the spatial distribution of radiation inside the sphere, which severely changes the sphere responsivity. To compensate this self-screening effect, we propose to use a specially designed auxiliary lamp whose illuminating area is spatially matched to that of the SLS under test. The validity of the proposed correction method is tested by numerical simulations based on the radiative transfer equation.